Visualization of weak confinement potentials by near-field optical imaging spectroscopy of exciton and biexciton in a single quantum dot

Imaging spectroscopy of a single GaAs interface fluctuation quantum dot (IFQD) was performed using a near-field scanning optical microscope (NSOM) with a spatial resolution of 40 nm. A difference in the emission profiles of an exciton and a biexciton was found for several IFQDs. By comparing with a numerical simulation based on the finite-difference time-domain method, this difference was attributed to the existence of a shallow potential dip in the IFQD. The NSOM wavefunction mapping for excitons and biexcitons as quasiparticles with different masses is a tool for investigating weak confinement potentials to detect local strain and disorder.